1. Field of the Invention
The present disclosure relates to displays and, more particularly, to a display substrate, and a method of manufacturing the display substrate.
2. Description of the Related Art
A typical liquid crystal display (LCD) apparatus includes a display panel and a driving part that applies a driving signal to the display panel. A gate driving circuit has been directly formed on an array substrate to decrease the thickness of the LCD apparatus and to simplify the manufacturing process for the LCD apparatus. For example, when a thin-film transistor (TFT) is formed on a display area of the array substrate, the TFT for driving the gate driving circuit is formed in a peripheral area surrounding the display area at the same time. An amorphous silicon (a-Si) TFT has been generally used, but a poly-silicon (poly-Si) TFT, which performs its function with a high driving speed and a high display quality, has become more desirable.
Methods for forming a poly-Si thin-film in the poly-Si TFT can include directly forming the poly-Si thin-film on a substrate, or heat-treating an a-Si thin-film formed on the substrate by a laser beam to form the poly-Si thin-film.
In the method of heat-treating by laser beam, the a-Si thin-film is liquefied to a liquid state when the substrate on which the a-Si thin-film is formed is irradiated by laser beam. Then, the liquefied silicon re-solidifies with a nucleus as the center, and is rearranged as multiple grains having superior crystalline quality. Thus, the a-Si thin-film can be transformed into the poly-Si thin-film having high electrical conductivity.
However, when the laser beam irradiates a front surface of the substrate, the a-Si thin-film adjacent to the substrate is less crystallized, such that on-current may decrease. To solve the problem, the power of the laser beam may be increased, or the thickness of the a-Si thin-film may be decreased. However, in those situations, a gate line may be damaged, or an etching process margin may be increased.